Binding elements constructed of plastic or metallic wires which have been helically or spirally coiled and successively passed through perforations in the rear margin of papers, such as sheets and covers to form books and notebooks in bound form, are well known.
A narrow gauge wire or plastic is used to form the spiral binding element requiring a close pitch or space between the adjacent coils to better resist deformation and permanent distortion of the designed shape. Commonly, there are some 35 to 45 coils in a typical 11.times.8.5 spiral bound notebook.
It is now understood that if no provision is made to securely anchor such coils, the coils may, due to friction encountered in turning the sheets, handling, etc., gradually creep outward at one end or the other.
In order to overcome this problem, the ends of the spiral coils, usually of metal but sometimes of plastic, are crimped or bent to prevent the coils from rotating as a result. The present spiral binding elements cannot be refilled without great difficulty and inconvenience to the user.
It has been proposed to overcome the above-mentioned problems by locating a removable locking element at each end of the spiral coils. One of the problems arising with prior art binders employing this arrangement is that the locking elements are of a configuration which interferes with the free and uninterrupted 360 degree rotation of the papers so as to allow the papers to lie flat for writing or drawing purposes. The effect is particularly objectionable where the locking elements provide transverse abutments that cannot pass through the perforations in the papers, and will therefore prevent removal of the binding element from the papers and thereby hold the papers in assembled relationship. Also, when such locking elements come into contact with portions of the sheets, binding or mutilation of the sheets is apt to occur.